The acute phase - the first 72 hours
Bleeding and swelling make the area red, hot and painful. Various
cells, including white blood cells and scavenger cells, are attracted
to the region to begin the process of cleaning up debris. These
cells also release chemicals which encourage fibroblasts to multiply
- fibroblasts are the cells which produce the proteins of repair,
especially collagen.
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Repair and regeneration depend on three major
factors: elimination of debris, the regeneration of endothelial cells, and the production
of fibroblasts, which compose connective tissue throughout the body and form the basis of
scar tissue.
Typically in a traumatic event injured blood vessels
become deprived of oxygen and die. Before repair and regeneration can occur, debris must
be removed.
Stimulated by a lack of oxygen, capillary buds begin
to form in the walls of the intact vessels. From these buds grow immature vessels that
form connections with other vessels. As these vessels become mature, more oxygenated blood
is brought to the injured area. Fibroblasts migrate to the injury and form collagen
substances, often within a few days. New protein fibres are laid down in a haphazard
manner. Once laid down, the scar tissue begins to contract.
Also during this stage, two types of healing occur.
Primary healing:
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healing by first intention
takes place in an injury that has even and closely opposed edges, such as a cut or
incision. With this type of injury if the edges are held in very close approximation, a
minimum of granulation tissue is produced. |
Secondary healing:
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healing by secondary
intention, results when there is a gaping lesion and large tissue loss, leading to
replacement by scar tissue. External wounds such as lacerations commonly heal by secondary
intention. |
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